There has been known a system that detects a moving object and continuously images the detected moving object. In this system, an area sensor device such as a laser distance meter is used to scan a monitoring area to detect a moving object and a camera device is used so as to track the detected moving object so that the moving object is continuously imaged. For example, Patent Literature 1 discloses a security system that turns a camera device so as to track an intruder, during which image data monitoring the intruder are obtained.